Thermally vaporisable fumigant comprising sensitized ammonium nitrate and a presticide



Patentcd Apr. 20, 1948 THERMALLY YAPOBISABLIB FUMIGANT COltflRISlNG SENSITIZED AMMONIUM 'NITRATE AND A PESTICIDE John Stocks Flanders, West Kiibride. and Elwyn Jones, Ardrossan,-

Scotland,

aaaignora to Im-" periai Chemical Industries Limited, a corporation of Great Britain No Drawing. Application April 1, 1946, Serial No. 658,882. In Great Britain June 4', 1945 The present invention relates to the art of fumigating with pesticidal compounds, and-more particularly to the provision of an improved composition for the thermal production of fumes of pesticidal compounds that are capable of vaporisation when suitably heated. The invention is especially valuable for the purpose of fumigating with combustible pesticidal compounds or pesticidal compounds easily decomposed when overheated. The invention, for instance, facilitates the economical production of a fume comprising an aerosol of the condensed vapour of a pesticidal compound which can deposit on the bounding surfaces of a closed space in which the fume is generated so as to produce a thin layer of the pesticidal compound that will be active long after the atmosphere is clear of the actual fumes.

One example of a pesticide capable of depositing such a layer when a suitable fumigation method is applied to volatilise it, is the powerful insecticide beta-beta- (para-dichlorophenyl) -alpha-alpha-alpha-trichloroethane (now more commonly designated 2,2-bis(parachlorophenyl) 1,1,1-trichloroethane) A further example is the still more powerful insecticide gamma-benzene hexachloride which can be applied in the form of a smoke by volatilisation from hot plates or by other heating methods. In co-pending British application No. 2074/44 there is claimed inter alia a method for fumigating an enclosed space. to control pests therein which comprises treating the said space with an aerosol containing a benzene hex-achloride.

A combustible candle fumigator, similar to the familiar sulphur candle, would be a very convenient means for producing the fumes of a vaporisable. pesticidal compound, but in the case of many pesticides it would not be possible to make up a candle in which a pesticide is drawn into a flame for the purpose of volatilising it, since the pesticide would thereby be decomposed or burned with the formation of useless decomposition or combustion products, whereas in the case of the sulphur candle the active material is the sulphur dioxide produced by the burning of the sulphur.

It is known that the thermal decomposition of ammonium nitrate can be sensitised by admix- 8 Claims. (Cl. 167-40) 2 and ammonium bichromate are examples of salts of chromic acid having this action.

The temperatures attained in the mass as the result of the reaction are, generally speaking, much below thoseexperienced in ordinary instances of combustion. The present invention is based on ,the discovery that while the heat vaporisable pesticidal compounds are typically oxidisable substances, and while ammonium nitrate contains, and the salt of chromic acid may contain. available oxygen (ammonium bichromate may be held not to contain available oxygen if its decomposition proceeds in a straightforward manner), the pesticidal compound can be vaporised without any substantial destruction when it is present in admixture in a composition undergoing thermal decomposition and comprising ammonium nitrate and a salt oflchromic acid adapted to render the ammonium nitrate in the mixture capable of such self-sustained exothermic reaction.

According to the present invention therefore the improved f umigating composition consists of a mixture comprising a thermally vaporisabie pesticidal compound, ammonium nitrate and an ammonium nitrate-sensitising salt of chromic acid in amount suilicient to render the composition capable of propagating throughout itself at ordinary atmospheric pressure an exothermal reture of the ammonium nitrate with various salts action when initiatedby local heating.

The said mixture may also include china clay.

A cartridge made up from the composition and provided with a waterproof casing may advantageously be employed, and such cartridge may advantageously include a small piece of fuse or of match composition or other ignitingcomposition in contact with the fumigating charge in order to facilitate the ignition of the latter from an ordinary domestic friction match. The fumigating charge is preferably in compact form, and for its production the pulverulent mixture of ingredients may be subjected to compression. Otherwise the mixture may be made into compact form with the aid of a binder or bonding agent, for. instance, a nitrocellulose composition, and may be extruded or moulded into form. The cartridge comprising the fumigating charge may conveniently bewrapped up in paper, and the wrapped cartridge dipped in wax or other waterproofing medium. l r

When a local portion of the charge is strongly heated by the ignition of the match composition or the like or 'the piece of fuse, or by touchin it with a piece of red hot metal or the like, a gas evolving decomposition accompanied by the evoasides:

lution of the pesticidal mine and little carbon I fume, if any. and quite unaccompanied by name will propagate itself through the charge. The fumigating charges provided according to the present invention are therefore both safe and convenient for application in confined space even when easily inflammable objects are present in the confined space.

""Etampled A fungicidal composition tobe u ediii powder form is made up as follows:

80 parts of afmixture consisting c1 90 parts.

. ammonium nitrateand 10 partspotassium chro- The invention is illustrated by the following examples, in which the parts mentioned are parts by weight.

Example 1 A mixture of 90 parts pulverised nitrate; 10 parts gamma-benzene hexachloride, and 10 parts potassium chromate in powder form is compactedby pressure into the-iorniota rod of about 1' centimetre diameter and-considerably I reater length. a small piece of being.

serted in the mixture so as to extend ifromon end of the rod inwardly for a considerable ijdis tance. The composite rod so obtained is wrapped} in manila paper and dipped inmolten paraflln wax melting at about 50 C. maintained-at a temperature not exceedingabout 75 C. The end provided with the fuse is marked so "that; the

wrapper can be broken to expose the end of the cartridge containing the fuse to use the cartridge. I

Emmple'z The procedure is the same as in Example 1 V except that in place of 10 parts gamma-benzene hexachloride there are employed 1 parts 22- bis(parachlorophenyl) -1,1,1-trichl0roethane:=

Example 3 I A mixture of 90 parts pulverised ammonium nitrate, parts gamma-benzene hexachlo'ride and 10 parts potassium chromate in powder form is mixedwith a nitrocellulose solution made from parts quarter second industrial nitrocellulose, 48 parts di-butyl phthalate and 2'parts diphenylwhen it .is desired mate. are mixed with 20 parts'of' the fungicide pentachlorophenol.

While we have shown several embodiments of our invention particnlarlywith reference to the use of solid pesticides ,we do not wish to be restricted specifically to these embodiments since many other forms of the invention may be made without departing frmn the spirit and ."thereof. For instanceitis frequently desirable to include a solid .dfluent v inthe' composition and althoughchina clay is "preferred for this purpose other solid inorganiediluents. may be emmove We claim? 1'. A'fumigati ng statute of a 1 mixture comprisingia thermally -vaporisable pesticidjai compound, ammonium nitrate and an ammonium nitrate-sensitising 'saltof chromicacid inamount sufficient to render the. composition capable of propagating throughout itself at ordinary atmospheric pressure an exothermal reaction when initiated by local heating.

2. A fumigating composition as claimed in 'claim 1 wherein the said mixture includes china clay. e

" 3. A fumigating composition as claimed in claim 1 in the form of a compressed pellet.

.4. A .fumigating composition as claimed in claim 3 wherein the compressed pellet is provided with a'waterproof casing. I

5'. A 'fumigating composition as claimed in claim 4 wherein the compressed pellet is provided with a small piece of igniting composition.

6. Azi'umigating composition consisting of a mixture comprising a v thermally vaporisable pesticidal compound, ammonium nitrate and an amine, the ratio of the amounts of the powder mixture and .of the nitrocellulose solution being :35 by weight. The resulting .paste-is'extruded. at suitably raised temperature not. exceeding 100 C. to'the desired diameter and cut into suit ammonium nitrate-sensitising salt of chromic acidin amount'suflicient to renderthe composition capable of propagating throughout itself at ordinary atmospheric pressure an .exothermal able lengths before it cools. A small bead oiv a;

match head composition in the form of a paste containing a solution of a binding agent is applied at one end of each of the cut rods,arid after this has been. dried off the rod is wrapped in Example 4 paper. 1 t

A fumigating composition to be used in'powder .5

reaction when initiated by local heating, the

composition being in the form of a compressed pellet, and the pellet being v provided with a small pieceoi igniting composition. 3- LA fumigating composition consistingoiv a mixture, omprising az-bismarachiorophenyli form is made up as follows: parts of a mixture consisting of parts ammonium nitrate andlO' potassium chromate, are mixed with 25 parts of a crude gammabenzene hexachloride; and 93 parts of the resultingmixture is mixed with! parts ofchina clay;

, t g Example 5 A fumigating. composition to form is madeup as follows: 7 '75 parts of'a mixtureconsistingof 90 parts be used in powder" ammonium nitrate and 10 parts potassium chromate, are mixed with 25 parts of pure gamma benzene hexa'chloride, and 97 parts of the resulting mixture is mixed with 3 parts of-china clay,

ride, ammonium nitrate I 1, ,.ltricliloroetliane, ammonium'nitrate and an f ammonium nitrate-sensitising' salt oi" chromic acid in amount-sunicientto render the composition} capable of propagating:throughout'itself at ordinary atmospheric pressure'an exothern'ial re- -action when initiated'by local heating.

:8}. A fulnlgating composition' -consisting oi a mixture -,comprising gamma benzenei hexacl lot t d by loc al heating. v n

JOHN ELWYN Jorms. 

